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Commit 4523b6ca authored by Masahiro Yamada's avatar Masahiro Yamada Committed by Greg Kroah-Hartman
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linux/bits.h: make BIT(), GENMASK(), and friends available in assembly 

commit 95b980d62d52c4c1768ee719e8db3efe27ef52b2 upstream.

BIT(),  GENMASK(), etc. are useful to define register bits of hardware.
However, low-level code is often written in assembly, where they are
not available due to the hard-coded 1UL, 0UL.

In fact, in-kernel headers such as arch/arm64/include/asm/sysreg.h
use _BITUL() instead of BIT() so that the register bit macros are
available in assembly.

Using macros in include/uapi/linux/const.h have two reasons:

[1] For use in uapi headers
  We should use underscore-prefixed variants for user-space.

[2] For use in assembly code
  Since _BITUL() uses UL(1) instead of 1UL, it can be used as an
  alternative of BIT().

For [2], it is pretty easy to change BIT() etc. for use in assembly.

This allows to replace _BUTUL() in kernel-space headers with BIT().

Link: http://lkml.kernel.org/r/20190609153941.17249-1-yamada.masahiro@socionext.com


Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 90ca51d1

include/linux/bits.h

+10 −7
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0 */

#ifndef __LINUX_BITS_H

#define __LINUX_BITS_H



#include <linux/const.h>

#include <asm/bitsperlong.h>



#define BIT(nr)			(1UL << (nr))

#define BIT_ULL(nr)		(1ULL << (nr))

#define BIT_MASK(nr)		(1UL << ((nr) % BITS_PER_LONG))

#define BIT(nr)			(UL(1) << (nr))

#define BIT_ULL(nr)		(ULL(1) << (nr))

#define BIT_MASK(nr)		(UL(1) << ((nr) % BITS_PER_LONG))

#define BIT_WORD(nr)		((nr) / BITS_PER_LONG)

#define BIT_ULL_MASK(nr)	(1ULL << ((nr) % BITS_PER_LONG_LONG))

#define BIT_ULL_MASK(nr)	(ULL(1) << ((nr) % BITS_PER_LONG_LONG))

#define BIT_ULL_WORD(nr)	((nr) / BITS_PER_LONG_LONG)

#define BITS_PER_BYTE		8
@@ -17,10 +19,11 @@ 
 * GENMASK_ULL(39, 21) gives us the 64bit vector 0x000000ffffe00000.

 */

#define GENMASK(h, l) \

	(((~0UL) - (1UL << (l)) + 1) & (~0UL >> (BITS_PER_LONG - 1 - (h))))

	(((~UL(0)) - (UL(1) << (l)) + 1) & \

	 (~UL(0) >> (BITS_PER_LONG - 1 - (h))))



#define GENMASK_ULL(h, l) \

	(((~0ULL) - (1ULL << (l)) + 1) & \

	 (~0ULL >> (BITS_PER_LONG_LONG - 1 - (h))))

	(((~ULL(0)) - (ULL(1) << (l)) + 1) & \

	 (~ULL(0) >> (BITS_PER_LONG_LONG - 1 - (h))))



#endif	/* __LINUX_BITS_H */